1. Field of the Invention
The invention relates to integrated circuit devices. More particularly, the invention relates to driver output stages of integrated circuit devices.
2. Description of the Related Art
The manufacturers of integrated circuit devices have always sought improved frequency response for their circuits, especially for circuits typically operating at higher frequencies, e.g., frequencies above 10 kHz. One technique used in attempting to enhance the frequency response of, e.g., amplifier circuits including those used in operational amplifiers, is a feedforward arrangement.
Feedforward arrangements are known process control arrangements in which changes are detected near the process input and an anticipating correction signal is applied before the process output signal is affected. For example, see Widlar et al., "Operational Amplifiers And Voltage Regulators", Digest of Technical Papers, 1985 IEEE International Solid-State Circuits Conference, which discloses an operational amplifier having a feedforward arrangement incorporated therein.
In the Widlar article, the feedforward arrangement includes a current modulator, formed by a pair of transistors, that modulates current added to the input drive current to the negative driver output transistor. However, such arrangement includes active components and also includes compensation to prevent oscillation of the circuit. Still, the arrangement suffers from problems such as stability (especially at higher frequencies, i.e., above approximately 10 kHz).
Accordingly, a simple, low cost feedforward arrangement is sought that enhances high frequency response, yet does not suffer from operational instability or the other problems associated with conventional feedforward arrangements.